1. Field of the Invention
The present invention relates to an image sensing apparatus and an image capturing system which capture an object image.
2. Description of the Related Art
A recent digital still camera mainly aiming at still image shooting uses image capturing elements corresponding to more than 10,000,000 pixels. A movie camera mainly aiming at moving image shooting also uses image capturing elements corresponding to millions of pixels. For these application purposes, generally, high-resolution shooting that requires a high resolution is executed using a large number of pixels. If the resolution can be low, shooting is executed using a small number of pixels. In high-resolution shooting, signals are read out from almost all pixels of the image capturing elements. In low-resolution shooting, readout is done while performing pixel decimation driving or pixel signal addition, thereby preventing battery drain in the camera, increasing the number of shot images, and executing high-speed shooting for moving images (Japanese Patent Laid-Open Nos. 9-46596 and 2001-36920).
Japanese Patent Laid-Open No. 9-46596 discloses a technique of adding signals of different colors on a common pixel amplifier.
Japanese Patent Laid-Open No. 2001-36920 discloses a technique of adding homochromatic signals so that spatial color arrangement of the colors after addition matches that before addition in every block of 4×4 pixels.
The technique of Japanese Patent Laid-Open No. 9-46596 does not adopt homochromatic addition and cannot obtain the signals of the respective colors. It is therefore impossible to obtain a high-resolution image.
In Japanese Patent Laid-Open No. 2001-36920, since the spatial centers of gravity of the pixels after addition are not located at equal pitches, moiré is generated.
As described above, in the conventional techniques, it is very difficult to obtain a high-resolution image by addition processing.